U.S. patent number 4,795,455 [Application Number 07/091,248] was granted by the patent office on 1989-01-03 for sanitary napkin pad liner.
This patent grant is currently assigned to Personal Products Company. Invention is credited to Thomas J. Luceri, John Lukjanczuk.
United States Patent |
4,795,455 |
Luceri , et al. |
January 3, 1989 |
Sanitary napkin pad liner
Abstract
A napkin pad liner is provided which is designed to be used with
a conventional sanitary napkin to provide more rapid fluid take-up
and reduced fluid strikeback. The liner includes a cover of a
non-wettable, fluid permeable hydrophobic material which covers a
thin layer of absorbent fabric. Pressure sensitive adhesive is
located on the napkin-facing side of the absorbent fabric. The
adhesive is protected prior to use of the liner by a release strip.
In a preferred embodiment the liner is embossed with a central
channel to promote rapid longitudinal fluid distribution at the
time of fluid take-up.
Inventors: |
Luceri; Thomas J. (Bridgewater,
NJ), Lukjanczuk; John (Milltown, NJ) |
Assignee: |
Personal Products Company
(Milltown, NJ)
|
Family
ID: |
22226791 |
Appl.
No.: |
07/091,248 |
Filed: |
August 31, 1987 |
Current U.S.
Class: |
604/386 |
Current CPC
Class: |
A61F
13/51108 (20130101); A61F 13/536 (20130101); A61F
13/474 (20130101); A61F 13/51121 (20130101); A61F
13/51305 (20130101); A61F 13/53717 (20130101); A61F
13/53747 (20130101); A61F 2013/51409 (20130101); A61F
2013/583 (20130101); A61F 2013/15382 (20130101); A61F
2013/51377 (20130101); A61F 2013/5147 (20130101); A61F
2013/51078 (20130101); A61F 2013/4708 (20130101); A61F
2013/53765 (20130101); A61F 2013/5055 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61F 13/56 (20060101); A61F
013/16 () |
Field of
Search: |
;604/385.1,386,385,378,389,390,379,382,370,366 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Yasko; John D.
Claims
What is claimed is:
1. A napkin liner for use in conjunction with a sanitary protection
product comprising:
a substantially non-wettable, fluid permeable cover of hydrophobic
material located on the body-facing side of the liner;
a thin layer of absorbent material for transmitting body fluids
which have passed through the cover material to an underlying
sanitary protection product;
adhesive means, located on the sanitary protection product facing
side of said liner, for attaching said liner to an underlying
sanitary protection product, said adhesive means posing a
relatively insubstantial barrier to the transmission of body fluids
through said liner to an underlying absorbent product; and
release strip means for covering said adhesive means to prevent
inadvertent adhesion of said liner prior to use.
2. The napkin liner of claim 1, wherein said liner is embossed with
a pattern.
3. The napkin liner of claim 2, wherein said embossed pattern
comprises a central, longitudinal channel.
4. The napkin liner of claim 3, wherein said central, longitudinal
channel has a width of approximately one-half inch.
5. The napkin liner of claim 2, wherein said embossed pattern
comprises a snowflake-like pattern evenly distributed over the
surface of said cover.
6. The napkin liner of claim 2, wherein said embossed pattern
comprises an hourglass-shaped channel.
7. The napkin liner of claim 6, wherein the surface of said cover
surrounding said hourglass-shaped channel is embossed with a
snowflake-like pattern.
8. The napkin liner of claim 2, wherein said embossed pattern
comprises two longitudinal channels respectively offset on either
side of the longitudinal center line of said liner.
9. The napkin liner of claim 1, wherein said adhesive means
comprises two lines of pressure-sensitive adhesive locate along the
longitudinal edges of said layer of absorbent material so as to
pose a relatively insubstantial barrier to the transmission of body
fluids through the center of said liner.
10. The napkin liner of claim 9, wherein said adhesive lines are
one-half inch in width or less so as to pose a relatively
insubstantial barrier to the transmission of body fluids through
the center of said liner.
11. The napkin liner of claims 1, wherein said cover material
comprises a thermally bondable material and said thin layer
includes thermally bondable fibers,
wherein said cover is thermally bonded to said thin layer about the
periphery of said liner.
12. The napkin liner of claim 11, wherein said thin layer comprises
a low density mixture of absorbent fibers and conjugate fibers.
13. The napkin liner of claim 12, wherein said thin layer comprises
a thermally bonded nonwoven fabric, and further includes
non-wettable polymeric fibers for maintaining the loft of said
fabric.
14. The napkin liner of claim 13, wherein said fabric comprises two
layers of a 2.0 oz./yd..sup.2 nonwoven.
15. A napkin liner for use in conjunction with a sanitary
protection product comprising:
a substantially non-wettable, fluid permeable cover of hydrophobic
material located on the body-facing side of the liner;
a thin layer of absorbent material for transmitting body fluids
which have passed through the cover material to an underlying
sanitary protection product;
adhesive means, located on the sanitary protection product facing
side of said liner, for attaching said liner to an underlying
sanitary protection product, said adhesive means posing a
relatively insubstantial barrier to the transmission of body fluids
through said liner to an underlying absorbent product; and release
strip means for covering said adhesive means to prevent inadvertent
adhesion of said liner prior to use;
wherein the longitudinal edges of said cover material overwrap the
longitudinal sides of said liner and the longitudinal edges of the
sanitary protection protection product facing side of said layer of
absorbent material; and wherein said adhesive means comprises two
lines of pressure sensitive adhesive located along the overwrapped
longitudinal edges of said cover material on the sanitary
protection product facing side of said layer of absorbent
material.
16. The napkin liner of claim 15, wherein said adhesive means
further comprises means for adhering the overwrapped longitudinal
edges of said cover material to the sanity protection product
facing side of said layer of absorbent material.
Description
This invention relates to products for absorbing body fluids and,
in particular, to liners for sanitary napkins.
In general, sanitary napkins and other absorbent products have an
absorbent core comprising one or more layers of fluid absorbent
material such as wood pulp, rayon, gauze, tissue or the like, and
in some cases synthetic hydrophilic material such as hydrophilic
polyurethane foam may be used. The hydrophilic material is
generally provided in the form of a pad, which may have a
rectangular or somewhat oval shape. To enhance the sense of comfort
for the user, absorbent products also generally employ a cover
material or facing which covers the body-facing surface of the
hydrophilic material. The cover is generally made of hydrophobic
materials so that it will not be stained by or absorb fluids. The
purpose of the cover is to structurally contain the loosely packed
absorbent material and to protect the body from direct contact with
the absorbent pad. To protect the clothing of the user from being
stained or wetted by the body fluids absorbed by the hydrophilic
material, the pad is generally backed by a body fluid impervious
barrier sheet. The absorbent product is positioned on the body with
the hydrophilic material facing the body and the fluid impervious
barrier facing the clothing of the user. To retain the product in
place during use, pressure-sensitive adhesive is conventionally
located on the outer surface of the fluid impervious barrier so
that the product may be adhered to the undergarment of the
user.
An ideal sanitary napkin should exhibit at least two favorable
characteristics. One is a fast fluid absorbency rate, or rapid
fluid take-up. At the moment when body fluids contact the cover,
the design and materials of the napkin should be such that rapid
transmission of the fluids through the cover to the underlying pad
is promoted. The fluids should be transmitted to the pad remote
from the cover and the body area it contacts as quickly as
possible.
A second desirable characteristic is low rewettability, or fluid
strikeback. Once a sanitary napkin has absorbed body fluids, the
materials and construction of the napkin should be such that the
fluids remain within the absorbent core, and are not retransmitted
back through the cover to contact the body of the user. A napkin
with a low rewettability characteristic will remain comfortable
during extended periods of use, even after absorbing a significant
amount of body fluids.
A third characteristic of varying necessity is the ability of the
product to retain a large volume of fluid. The nee of the user for
this characteristic may vary from day to day, or even from hour to
hour. During times of light flow or between menstrual periods, a
user may need only minimal protection, and hence may prefer to use
one of the commercially available thin, protective absorbent
napkins, such as that described in U.S. Pat. No. 4,518,451. At such
times the thin napkin can provide adequate protection against the
soiling of undergarments, while affording a high degree of comfort
and a very low profile under clothing.
At other times, however, a user may require a bulkier, more
substantial napkin which is capable of absorbing significant
amounts of fluid. Finally, there can be times when the user's needs
may be variable or uncertain. At those times a user may initially
employ a thin napkin, but may need to carry one of the bulkier,
more substantial napkins in reserve. Such is not always convenient,
however. It would be desirable, then, for a user to carry a
thinner, more convenient product which may be used to supplement a
thin napkin when the need arises.
In accordance with the principles of the present invention, a
sanitary napkin pad liner is provided which may be used in
conjunction with any other sanitary napkin. A preferred embodiment
of the present invention includes a non-wettable, fluid permeable
cover of hydrophobic material. The cover is embossed or laminated
to a layer of an absorbent nonwoven material. Located on the
napkin-facing side of the nonwoven material is a pressure sensitive
adhesive which is sufficient to maintain good contact between the
nonwoven material and the sanitary napkin to which it is designed
to be adhered. The adhesive area is minimized and selectively
located so as to present an insubstantial barrier to fluid
transmission. A release strip is placed over the adhesive to
protect it from contamination and inadvertent adhesion prior to
use.
In a most preferred embodiment, the sanitary napkin pad liner of
the present invention includes an embossed pattern on the cover
surface. Embodiments of the present invention, when used with a
conventional sanitary napkin, have been found to significantly
increase the absorbency rate while providing a decrease in fluid
strikeback as compared with the conventional sanitary napkin
alone.
In the drawings:
FIG. 1 is a perspective view of a sanitary napkin pad liner
constructed in accordance with the principles of the present
invention showing both major surfaces of the liner;
FIG. 2a is a cross-sectional view of a sanitary napkin pad liner
constructed in accordance with the principles of the present
invention;
FIG. 2b is a cross-sectional view of the sanitary napkin Pad liner
of FIG. 1, taken along lines 2--2 thereof;
FIGS. 3a-3c illustrate various embossing patterns suitable for use
by the liner of the present invention; and
FIG. 4 illustrates a technique for embossing a sanitary napkin pad
liner of the present invention with a central channel.
Referring to FIG. 1, a sanitary napkin pad liner constructed in
accordance with the principles of the present invention is shown.
The liner comprises a hydrophilic cover 12 embossed to a high bulk
absorbent nonwoven fabric 14. In a preferred embodiment the cover
12 is a coextruded apertured film of two polymeric materials. The
outer, body contacting layer comprises essentially linear low
density polyethylene, and the inner, fabric contacting layer
comprises essentially an ethylene-vinyl acetate (EVA) copolymer.
Both layers contain other additives, as described in U.S. patent
application Ser. No. 840,290, filed Mar. 14, 1986. A Preferred
cover material has an average open area of about 42%, a thickness
of about 4.5 mils, and a basis weight of about one oz./yd..sup.2
This cover material is preferred for the ability to achieve heat
sealing by melting the inner EVA layer to its melting point, which
does not cause the polyethylene layer to melt. The unmelted
polyethylene layer thereby maintains the integrity of the film and
its apertures during a heat sealing process.
A preferred material for the absorbent nonwoven fabric 14 is a low
density, thermally bonded nonwoven fabric comprising a mixture of
absorbent fibers, non-wettable polymeric fibers, and conjugate
fibers. The absorbent fibers may be wood pulp or other cellulosic
fibers which may be treated to enhance absorbency. Suitable
conjugate fibers comprise a fiber of a polyester core surrounded by
a sheath of polyethylene, and suitable non-wettable polymeric
fibers comprise polyester. A highly satisfactory absorbent fabric
is provided by a thermally bonded absorbent fabric comprising 44%
by weight of wood pulp fibers, 43% by weight of conjugate fibers
having a staple length of 3.8 cm and a denier of 3.0, and 13% by
weight of polyester fibers having a staple length of approximately
2 in. and a denier of 15. The fabric is stabilized by passing hot
air through the fibers and thereby melting the Polyethylene sheaths
of the conjugate fibers, which bonds the fabric together upon
cooling. Thus it is seen that the conjugate fibers provide
integrity for the fabric, the wood pulp provides the desired
absorbency, and the polyester fibers maintain the loft of the
fabric and its fluid transmitting capillaries between fibers when
the wood pulp is saturated with fluid.
Preferably, the layer 14 of absorbent fabric comprises two layers
14 and 15 of a 2.0 oz./yd..sup.2 fabric, as shown in the
cross-sectional views of FIGS. 2a and 2b. The two layers are in
intimate contact with each other so as to provide a continuous
capillary path between the cover 14 and the conventional napkin to
which the pad liner is attached. The contact between the two layers
and the cover is enhanced and maintained through bonding as
described subsequently.
In the embodiment of FIG. 1, the cover material is trimmed flush
with the ends of the absorbent fabric 14 at the longitudinal ends
of the liner. The cover material at the longitudinal sides 11 and
13 of the liner is folded around the sides of the liner and extends
slightly onto the underside of the absorbent fabric. Along the
edges of the cover material on the underside of the liner are two
lines 16 and 18 of a highly aggressive pressure sensitive adhesive,
such as Fuller 6680 hot melt adhesive. These positioning adhesive
lines provide a means for attaching the pad liner to a conventional
sanitary napkin. The adhesive lines should be narrow (i.e., 0.25
inches or less in width), since they represent a barrier to fluid
passing through the pad liner to the underlying sanitary napkin.
Preferably the adhesive lines extend in broken or unbroken lines
along nearly the entire length of the pad liner, so that intimate
contact will be maintained between the absorbent fabric 14 and the
face of the underlying sanitary napkin, thereby ensuring good fluid
transmissivity.
Covering the adhesive lines is a protective release strip 20 which
is provided to protect the adhesive lines from contamination and
unintended adhesion prior to use. A particularly useful material is
a semibleached kraft paper, the adhesive contacting side of which
has been silicone treated to Provide easy release from the adhesive
lines 16 and 18.
The napkin pad liner of FIG. 1 is embossed along nearly the entire
length of the center of the napkin to form a central channel 22. In
a constructed embodiment the central channel 22 had a width of 0.25
inches. The embossed channel not only maintains the integrity of
the liner by embossing the cover and absorbent fabric layers
together, but it also provides enhanced rapid fluid absorbency and
low rewettability characteristics. As compared with other embossing
patterns, discussed below, the central channel enhances absorbency
by directing rapid deposits of fluid along the channel, from which
the fluid is quickly transmitted through the liner. This minimizes
fluid build-up at a particular region of the liner and a resultant
deposit of fluid in only a limited region of the underlying
sanitary napkin. The central channel also minimizes the possibility
of fluid transmission laterally to the sides 11, 13 of the
liner.
A constructed embodiment of the liner of FIG. 1 measured 1.8 inches
wide by 7.6 inches long. These dimensions were chosen so that the
liner was sized to correspond with the absorbent face dimensions of
most commercially available sanitary napkins.
FIGS. 2a and 2b show cross-sectional views of two napkin pad liners
of the present invention. In these FIGURES, the cover and absorbent
fabric layers are shown separated for clarity of illustration; i
should be understood that the separation of materials does not
occur in the embossed liner. In FIG. 2a, the cover 12 and absorbent
fabric layers 14 and 15 are all of substantially the same width.
The longitudinal edges 11, 13 of the liner are sealed by thermal
bonding, as indicated at 24 and 26. The preferred materials readily
afford this construction technique, as the EVA layer of the cover
14 melts and bonds to the conjugate fibers of the absorbent fabric.
FIG. 2b is a cross-sectional representation of the FIG. 1
embodiment, in which the cover 14 wraps over the longitudinal edges
11 and 13 of the liner. It should also be noted that when the hot
melt adhesive lines 16 and 18 are applied along the edges of the
cover material, the adhesive will pass through the apertures of the
cover 14 and adhere the cover edges to the absorbent fabric 14.
Thus, the absorbent fabric is securely enveloped by the cover.
FIGS. 3a, 3b, and 3c illustrate alternative embossing patterns
suitable for use in a napkin pad liner of the present invention.
FIG. 3a illustrates a liner with an evenly distributed embossed
snowflake pattern. The Pattern is embossed in the manner shown in
U.S. Pat. No. 4,518,451, with the snowflakes spaced from each other
approximately in half-inch spacing. FIG. 3a shows only portions of
the embossing; in practice, the pattern covers the entire liner in
an even distribution. The snowflake pattern provides depressions in
which body fluids may collect for rapid transmission through the
liner.
FIG. 3b illustrates an hourglass-shaped embossing, with the area of
the liner surrounding the hourglass embossing containing the
snowflake embossing. The unembossed area within the hourglass
channel maintains a high loft for rapid absorbency of body fluids,
unimpeded by thermally compressed and melted areas resulting from
embossing. Undesired lateral transmission of body fluids is
retarded by the surrounding hourglass channel.
FIG. 3c illustrates the use of two quarter-inch embossed channels
entending along opposite sides of the longitudinal center line of
the liner.
Embodiments using these three embossing patterns and the central
channel of FIG. 1 were all constructed and tested with conventional
sanitary napkins for absorption time and rewet capacity. While all
embossing patterns were found to enhance these characteristics,
particularly absorption time, the greatest improvement was provided
by the central channel with its longitudinal fluid distribution
property.
The embodiment of FIG. 1 with its central channel was constructed
and tested with several commercial sanitary napkins to demonstrate
the improved performance provided by tee present invention. Table A
shows these test results. The test results are a summary of several
individual tests of each napkin or napkin and liner combination. In
each case, the napkin pad liner was attached in the manner of its
intended use, which is to align the liner with the face of the
napkin and secure it to the napkin with the lines of adhesive. The
napkin, or the napkin and liner combination, was then saturated by
depositing 15 cc of synthetic menstrual fluid on the upward facing
cover of the napkin or combination. The time required for the
tested item to absorb the fluid was noted and recorded as a 15 cc
absorption time. The saturated item was then covered with tissue of
a known weight and a plexiglas plate, and a pressure of 0.55
lbs./in..sup.2 was applied to the plate for approximately 3 minutes
to induce rewet. The plate was removed and the tissue weighed to
determine the amount of fluid which was retransmitted through the
cover and absorbed by the tissue. This fluid weight was recorded as
the 15 cc rewet amount in grams. The test results of Table A show a
significant improvement in fluid absorbency time and in rewet
values provided by the combinations of the commercial napkins and
the liner .COPYRGT.f the present invention as compared with these
properties of the commercial napkins alone.
TABLE A ______________________________________ 15 cc Absorp- Rewet
tion Time 15 cc Product/Combination (sec.) (grams)
______________________________________ SURE & NATURAL .RTM.
Napkin alone 17.4 3.8 SURE & NATURAL .RTM. Napkin/Liner 8.6 2.3
New Freedom .RTM. Thins napkin alone 58.1 5.2 New Freedom .RTM.
Thins napkin/Liner 11.9 2.5 Tampax Maxithins .RTM. Napkin alone
11.7 3.2 Tampax Maxithins .RTM. Napkin/Liner 7.7 0.6
______________________________________
The foregoing test results demonstrate that, since the napkin pad
liner of the present invention improves the absorbency rate for
commercially available sanitary napkins, it is expected that a user
will experience a reduced incidence of failure. This is because one
mechanism of napkin failure is a rapid deposition of fluid at a
rate greater than the rate at which the napkin can absorb the
fluid. When this occurs, the fluid can puddle on the napkin surface
and flow laterally beyond the sides of the napkin face before it
can be absorbed. The napkin pad liner of the present invention
improves the rate of absorbency, thereby reducing the instances of
failure by this mechanism.
Second, because the napkin pad liner of the present invention
reduces rewet, the user should stay drier during use. The napkin
pad liner acts to keep a greater amount of the absorbed fluid away
from the surface of the liner cover, and away from the user's body.
Additionally, the preferred apertured film cover provides a cleaner
appearance after the liner is used than does the cover of many
commercially available napkins.
Third, a distinct advantage of the napkin pad liner of the present
invention is that a user can select when to use it. For instance,
the user may elect to use the liner with her normal sanitary napkin
during heavy flow days, while dispensing with the liner during
light flow days when a rapid absorbency rate may not be required.
Furthermore, the thin liner may be conveniently carried by the user
in a pocket or purse.
FIG. 4 illustrates a technique for embossing the central channel 22
in the napkin pad liner of FIG. 1. In FIG. 4, an embossing roller
40 is shown in cross-section with a central raised area 42. The
embossing roller 40 opposes a smooth anvil roller 42 with a nip 44
therebetween. Positioned between the rollers and within the nip is
the napkin pad liner 10. The two rollers are adjustably spring
loaded so as to urge them together and close the nip 44. By virtue
of the spring loading the two rollers are urged together, and are
separated by a distance corresponding to the resistance to
compressive forces of the liner materials. In the nip area, the
liner is compressed to its limiting value, thereby forming the
central channel 22. The embossing process may be conducted using an
embossing roller surface temperature in the typical range of
93.degree.-121.degree. C., a set gap between the anvil and
embossing rollers of about 0.0025 cm., and an embossing pressure in
the nip area in excess of 500 lbs./linear inch.
* * * * *